Until recently, carburetors have been utilized on automobile internal combustion engines to regulate the quantity of fuel and air delivered thereto to produce power over a wide speed range. Recently, electrically controlled fuel injection systems have been used in association with throttle body housings. The throttle body housing has an inlet passage therethrough with a pivoted throttle blade to control the volume of air delivered to the engine. The fuel injector is controlled by an electrical signal to produce an adjustably variable fuel spray into the inlet passage of the throttle body. This regulates the necessary quantity of fuel to mix with air flowing through the throttle body as regulated primarily by the throttle blade.
For many years, the carburetor has been satisfactory in providing a desired control of air and fuel for engine operation. The recent emphasis on stringent fuel economy, further decreased exhaust emissions and an upward trend in fuel volatility has focused attention on the weakness of carburetors.
The aforementioned electrically controlled fuel injector in a throttle body produces superior fuel economy by very accurately controlling air/fuel ratios. The subject fuel injection system is superior to over-throttle fuel injection systems currently used principally due to a higher degree of fuel atomization at idle.
It would be desirable to provide a fuel system combining the characteristics of the fuel injector and a carburetion system to thus produce a relatively low cost and efficient fuel system for internal combustion engines.
In a basic electrically controlled fuel injection system which is currently used, a fuel injector is mounted within a throttle body and produces a variable duration spray of fuel into the air passage which leads to the engine's combustion chambers. The fuel injector is typically located to spray fuel directly into the inlet passage upstream or above the throttle blade of the throttle body. Patents which illustrate this type of arrangement are U.S. Pat. No. 4,458,650 and U.S. Pat. No. 4,503,826. This basic arrangement is generally satisfactory, but is not particularly effective in producing good fuel atomization when the engine is idling.
A slight modification of the above described basic fuel injection system is found in U.S. Pat. No. 4,442,818 and U.S. Pat. No. 4,475,518. In this modification, a fuel injector is mounted in the throttle body for injection above the throttle blade for higher speed operation, but another electrically controlled fuel device controls a bypass circuit during idle operation of the engine.
Another modification of the basic fuel injection system is found in U.S. Pat. No. 4,276,862. It discloses a throttle body with a fuel injector mounted to spray fuel into the air passage upstream of the throttle blade and includes means to facilitate idle operation of the engine. The means includes a bypass of circuit of the throttle blade controlled by an adjustable needle valve for regulating the mexture of fuel with air. This type of idle control is like use in previous carburetion systems.
Lastly, a modification of the basic fuel injection system is found in U.S. Pat. No. 4,495,802, which discloses an electrically controlled injector to introduce fuel to the inlet passage downstream from a throttle blade. The patent does not disclose any alternate or separate means to introduce fuel and air during engine idle. Other arrangements of a fuel injector within a throttle body are shown in the following U.S. Pat. Nos. 4,395,989; 4,406,266; 4,508,091; 4,509,483; and 4,524,743. The aforementioned patents are similar in that the throttle body uses an electrically controlled injector to spray fuel into the passage at a location downstream from a throttle blade. The introduction of the fuel is through a spray bar means or the equivalent located downstream from the throttle blade. This would appear to be ineffective, particularly during idle and wide-open-throttle operation.
It is desirable to combine the superior fuel atomization characteristics of this fuel injection system, particularly at idle, with a means to control cylinder-to-cylinder distribution at wide-open-throttle. However, it has been found that the direct injection of fuel into the air passage against a substantially closed throttle blade produces undesirable fuel atomization. Therefore, the introduction of fuel and air downstream from the throttle blade is desirable during idle. On the other hand, it has been found that excellent fuel atomization and cylinder-to-cylinder distribution is achieved by directing fuel spray from the injector to a venturi means located upstream or before the throttle blade, particularly at higher engine speeds when the throttle blade is toward a wide-open position. Consequently, the subject system utilizes an electrically controlled fuel injector mounted to spray fuel into a cavity communicated by a first opening therefrom through a first passage into the air passage of the throttle body at a location below the throttle blade. The first passage means is utilized for idle and part-throttle during relatively low speed engine operation. A second opening and passage to the cavity is connected to a venturi means or device located in the throttle body at a location upstream or before the throttle blade. When the throttle blade is in a more nearly open position and, consequently, the air flow through the throttle body increases significantly, fuel passes from the cavity through the second passage to the venturi means where the fuel is effectively mixed with air flow passing therethrough. Thus, fuel is thoroughly atomized and mixed with air during the mid and higher speed operation of the engine.
From the above discussion, it is clear that the subject fuel injection system utilizes a dual fuel passage system extending from the electrically controlled fuel injector. The dual passage system automatically changes from the introduction of fuel below the throttle blade during idle or low speed engine operation to the introduction of fuel through a venturi means located upstream of a throttle blade during higher speed engine operation.
Further advantages and features of the subject invention will be more readily apparent from a detailed description of the subject fuel injection system as described hereafter, reference being had to the accompanying drawings in which preferred embodiments are illustrated.